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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var str = 'abcoefoxyozzopp';
        var count = 0;
        for (var i = 0; i < str.length; i++){
            if(str[i] == 'o'){
                console.log('o出现的索引值（下标）' + i);
                count++;
            }
        }
        console.log('o出现的次数' + count);
    </script>
</body>
</html>